Masato (masato de yuca) is a thick, mildly sour, lightly alcoholic drink made by fermenting cooked cassava (yuca). It comes from Indigenous communities of the Amazon lowlands – in Peru, Ecuador and neighboring countries – where it’s drunk every day and shared at gatherings, and it’s also sold in towns of the Peruvian Amazon. It’s a relative of other South American cassava drinks, such as Ecuador’s chicha de yuca and Brazil’s cauim, and different from the Andean corn beer chicha de jora.
Why Masato Was Made by Chewing
Yeasts can’t ferment starch directly – it has to be broken down into sugars first. Beer brewers use malted grain for this. In the traditional masato method, some of the cooked cassava is chewed and returned to the pot: the enzyme amylase in saliva breaks down part of the starch into sugars that yeasts and bacteria can use. That’s why searches for “masato saliva” are common. Many makers today, especially in towns, skip the chewing and add sugar or sweet potato instead, which gives the microbes sugar to start on.
The Microbes
Masato is a spontaneous, mixed fermentation. Lactic acid bacteria sour it and yeasts make a little alcohol and fizz. From Peruvian masato de yuca, researchers isolated Lactiplantibacillus plantarum, Limosilactobacillus fermentum, Pediococcus acidilactici and Weissella confusa (Rebaza-Cardenas et al., 2023). In Ecuadorian chichas, including chicha de yuca, Saccharomyces cerevisiae and Torulaspora delbrueckii were the main yeasts (Piló et al., 2018). Some of the bacteria showed probiotic potential in lab tests, but there are no human studies of masato itself.
Cassava Safety
Raw cassava contains cyanogenic glycosides, which release cyanide. Food Standards Australia New Zealand requires cassava to be labeled as needing to be peeled and fully cooked before eating (FSANZ). For masato, peel the root completely, boil it until very soft, discard the cooking water, and don’t use a root that tastes bitter.
How Masato Is Drunk
- Young masato (a day or so) is sweet and barely sour.
- After 2–4 days it’s sour, lightly fizzy and mildly alcoholic – the usual stage.
- Longer ferments get more sour and stronger.
- It’s thinned with water just before serving and often drunk with the pulp in it.
Because it contains alcohol that increases with time, masato isn’t suitable for children, during pregnancy or for anyone avoiding alcohol. For more South American ferments, see a review of the region’s artisanal fermented foods (Jimenez et al., 2022); for West Africa’s cassava staple, see gari.